1. Field of the Invention
The present invention relates to traffic managing apparatus for supplying data files to requesting stations. The present invention also relates to a method of supplying data files to a plurality of requesting stations by accessing serving devices.
2. Description of the Related Art
Traffic management systems for providing load balancing are known, as described in United Kingdom patent number 2 413 868 and United Kingdom patent number 2 414 136, both in the name of the present applicant. Traffic management systems of this type are deployed when very high demands are placed upon particular websites. Thus a website, in the form of one or more HTML files, may be duplicated across many servers, groups of which may be clustered together with access being provided over a local network. An incoming request for the file is initially sent to the traffic management processor which is then responsible for selecting a particular server, possibly in a round robin fashion, issuing a request to the selected server over the local network and then accepting the requested file, so that it may be in turn sent back to the requesting station.
When installing a system of this type, it is necessary to make an estimate of the expected level of demand so that web pages will be returned in an acceptable period of time and a requesting station will therefore experience an acceptable grade of service. An acceptable grade of service for example may state that having issued a request to a server, the requested file should start to be received from the server within two seconds. Thus, if 90% of files are returned within this two second period, the grade of service may be considered acceptable. Consequently, the provision of hardware in order to achieve this grade of service should be good enough, given that excessive redundancy would be expensive and ultimately lead to the operation being uncompetitive.
Given these constraints of providing a level of service that is good enough, problems occur when excessive demand is placed on a particular website. For an information based website, excessive demand may occur when a particular event takes place. Similarly, for a commercial website excessive demand may occur when special offers are available or as a result of a successful advertising campaign. Under these circumstances, an unexpected level of demand may be placed on the website resulting in a substandard level of service which may result in customers waiting too long or, ultimately, in requests being lost. Such an experience may have detrimental side effects in that customers may be reluctant to access the website again and these would include regular customers.